The night before serving, begin the waffle batter: In a large bowl or deep plastic container, combine the yeast, sugar, buttermilk, butter, salt, and flour with a whisk. Beat hard until smooth, about 1 minute. Cover with plastic wrap and let rest in the refrigerator overnight.

In the morning, preheat the oven to 250º. Heat a waffle iron to medium-high heat and brush with oil to prevent sticking. Beat the eggs, vanilla, and baking soda into the batter with a whisk until evenly incorporated. Ladle 1/2 cup batter into the center of the iron, close the lid, and cook until crisp and golden, about 2 minutes. Place each waffle in the warm oven in a single layer until the rest of the waffles are baked. Serve warm with one or more of the suggested accompaniments.

To store, cool the waffles completely on a wire rack, wrap in plastic and then aluminum foil or plastic freezer bags, and freeze for up to 1 month.

Reheat frozen waffles in a toaster without thawing.